JP2003241558A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device capable of surely separating a fixed sheet from the surface of a fixing belt. <P>SOLUTION: The fixing device is provided with: a fixing roller 24; a pressurizing roller 26 in rotation contact with this fixing roller 24 with prescribed pressure; a heating roller 28 arranged away from the fixing roller 24; a fixing belt 32 bridged endlessly between this heating roller 28 and the fixing roller 24; and a heater 30 which heats the fixing belt 32 to heat unfixed toner on a sheet passing through the rotation contact part of the fixing roller 24 and the pressurizing roller 26. Then, the sheet carrying the unfixed toner on its surface passes through the rotation contact part along a single direction, thereby the unfixed toner is fixed onto the sheet. A separation guide member 70 which separates the fixed sheet from the fixing belt 32 and guides it in the direction of an exit is provided on a down stream about the traveling direction of the sheet compared with the rotation contact part. A space between the separation guide member 70 and the paper through area of the fixing belt 32 is set to be ≥0.2 mm and ≤2.0. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device used in a copying machine, a printer, a facsimile, etc., for melting and pressure-bonding unfixed toner on a sheet and fixing it on the sheet.

[0002]

2. Description of the Related Art Recently, in a fixing device for an electrophotographic apparatus, for example, Japanese Patent Application Laid-Open No. 6-318001 (Patent Registration No. 2)
No. 81297), a heat source is taken out from a two-roller type heating / fixing roller, a heating roller having a built-in heat source is separately provided, and heat from this heating roller is transferred to a fixing roller via a fixing belt. A so-called horizontal belt-type fixing device has been developed and put into practical use, which is transmitted to a rolling contact portion with a pressure roller to heat the roller.

According to this belt type fixing device, since the heat source is taken out from the fixing roller (heating / fixing roller in the two-roller type), the fixing roller can be constituted by a so-called soft roller. With the configuration of the pressure roller as a hard roller, the shape of the rolling contact portion (nip portion) between the fixing roller and the pressure roller can be a so-called downward (convex upward) nip shape. As a result, the unfixed sheet is deformed in accordance with the downward nip shape when passing through the nip portion, and is discharged in the state in which the downward deforming force is received from the nip portion. . Further, in the above-mentioned belt type fixing device, since the fixing belt is arranged close to the guide plate which defines the conveying path of the unfixed sheet, the fixing belt is conveyed by the radiant heat from the fixing belt. The unfixed sheet present can be preheated, which allows the temperature of the nip portion to be set low. Then, by using the fixing belt having a small heat capacity, the temperature of the fixing belt is rapidly cooled when passing through the nip portion, and the cohesive force of the toner separating from the fixing belt at the exit of the nip portion is increased, so that the fixing belt and the toner are separated from each other. It has a structure that can improve the releasability of.

In this way, due to the downward nip shape and the increased toner cohesive force, this belt-type fixing device can produce a clear fixed image without offset even when oilless or a small amount of oil is applied. It is known as a fixing device that solves the problems of releasability and oil application that cannot be solved by the two-roller system, such as obtained, and can be put to practical use.

[Problems to be Solved by the Invention]

On the other hand, in recent years, there has been a demand for an increase in the number of sheets processed per minute, and in order to achieve this, a higher transport speed is required. For this reason, in the belt-type fixing device, for example, a heating roller is arranged above the fixing roller and the pressure roller as disclosed in Japanese Patent Application Laid-Open No. 11-240410 filed by the applicant of the present application. A so-called vertical type belt-type fixing device has been proposed, and efforts have been made to cope with high speed.

However, while the conventional belt-type fixing device has the above-mentioned characteristics, in the type in which the releasing oil is applied to the outer peripheral surface of the fixing belt, there is a problem that oil adheres to the sheet surface. Various problems have been pointed out, such as a high cost for applying oil and a disadvantage of on-demand due to heat absorption due to contact of the oil applying roller with the fixing belt. Further, in the type in which the releasing oil is not applied to the outer peripheral surface of the fixing belt, there is no problem as long as normal print content is obtained, but in particular, there is a problem that the peelability of the sheet on which a solid image is printed from the fixing belt is poor. It has been pointed out.

The present invention has been made in view of the above-mentioned circumstances, and a main object of the present invention is to provide a fixed sheet,
An object of the present invention is to provide a fixing device that can be reliably peeled from the surface of a fixing belt.

Another object of the present invention is to provide a solid printed sheet without any adverse effect without providing a contact peeling member such as a peeling claw in the sheet passing area of the fixing belt. Another object of the present invention is to provide a fixing device that can be peeled from the surface of the fixing belt.

[0009]

[Means for Solving the Problems]
According to a first aspect of the present invention, in a fixing device according to the present invention, a fixing roller, a pressure roller that contacts the fixing roller at a predetermined pressure, and a fixing roller that is separated from the fixing roller. A heating roller provided, a fixing belt endlessly wound around the heating roller and the fixing roller, and the heating of the fixing belt, and the sheet passing through the rolling contact portion of the fixing roller and the pressure roller. A sheet having an unfixed toner carried on the surface thereof, passing through the rolling contact portion in one direction, thereby fixing the unfixed toner on the sheet. In the fixing device, a peeling guide member is provided on the downstream side of the rolling contact portion in the traveling direction of the sheet, the peeling guide member that peels the fixed sheet from the fixing belt and guides the sheet in the exit direction. The gap between the sheet passing area of the peeling guide member and the fixing belt, is characterized in that it is set to 2.0mm or less in the range of 0.2 mm.

According to a second aspect of the fixing device of the present invention, the peeling guide member is constituted by a part of a paper discharge guide plate.

According to a third aspect of the fixing device according to the present invention, the peeling guide member is fixedly arranged.

According to a fourth aspect of the fixing device of the present invention, the peeling guide member is separated from the outer peripheral surface of the fixing belt over the entire area.

According to a fifth aspect of the fixing device of the present invention, the peeling guide member is provided with a non-contact portion which faces the sheet passing region of the fixing belt, and the fixing device. And a contact portion arranged so as to face a non-sheet passing area of the belt.

According to a sixth aspect of the fixing device according to the present invention, the contact portion of the peeling guide member is
It is characterized by being formed of a heat resistant resin having slidability.

According to a seventh aspect of the fixing device according to the present invention, the contact portion of the peeling guide member is
It is characterized by being covered with a fluororesin.

According to the eighth aspect of the fixing device of the present invention, the peeling guide member is rotatably supported around an axis parallel to the rotation axis of the fixing roller, and the contact is made. It is characterized in that the portion is rotationally biased by a biasing member so as to come into contact with the non-sheet passing area of the fixing belt.

According to a ninth aspect of the fixing device of the present invention, the part of the peeling guide member that defines the gap is a line segment that connects the part to the central position of the fixing roller. It is characterized in that an angle formed by a line segment connecting the central position of the fixing roller and the central position of the pressure roller is set in a range of 30 to 60 degrees.

According to a tenth aspect of the present invention, in the fixing device according to the present invention, the outermost circumference of the fixing belt is
It is characterized in that a release layer is provided.

According to the eleventh aspect, the fixing device according to the present invention is characterized in that the release layer contains a fluororesin.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The structure of an embodiment of a fixing device according to the present invention will be described below in detail with reference to the accompanying drawings.

{Schematic Description of Fixing Device 10} First, as shown in FIG. 1, the fixing device 10 of this embodiment is fixed as a housing structure to an electronic image forming apparatus (not shown) such as a frame of an electronic printer. Housing 1
Equipped with 2. The housing 12 includes a bottom plate 14 directly fixed on the device frame, and side plates 16 standing upright from both front and rear edges of the bottom plate 14. Incidentally, although FIG. 1 is drawn as a front view and the details will be described later, the unfixed sheet having unfixed toner carried on the upper surface is conveyed from the right side to the left side in the drawing through a conveyance mechanism (not shown). It is set to be transported.

A sliding bracket 18 on which a heating roller 28, which will be described later, is rotatably supported is slidably mounted on the upper side of the housing 12 with respect to both side plates 16 in the vertical direction in the figure. Is attached to. Further, a swing bracket 20 on which a pressure roller 26, which will be described later, is rotatably supported is rotatably supported around the support shaft 22 with respect to both side plates 16 in the lower part of the housing 12. It is supported by a plate.

The fixing device 10 has, as a roller structure, a fixing roller 24 rotatably supported on both side plates 16 so as to be rotatable about a fixed axis, and substantially below the fixing roller 24 (specifically, left in the drawing). Of the fixing roller 24 and the pressure roller 26 rotatably supported by the swing bracket 20 around a fixed axis set parallel to the fixed axis of the fixing roller 24 in a state of rolling contact with the fixing roller 24 at an angle. The heating roller 28 is rotatably supported by the sliding bracket 18 in a state of being positioned substantially above.

Further, the fixing device 10 includes the heating roller 2
8, a heating source 30 such as a halogen lamp, and a fixing belt (heat transfer belt) 32 wound endlessly around the fixing roller 24 and the heating roller 28.
And are further equipped.

At the exit side of the rolling contact portion between the fixing roller 24 and the pressure roller 26 (that is, the downstream side in the sheet conveying direction), the fixed sheet passing therethrough is guided to the sheet discharge port. A pair of upper and lower discharge guide plates 40
A and 40B are arranged in a vertically separated state. One end of each of the sheet ejection guide plates 40A and 40B on the upstream side in the sheet conveying direction is arranged close to the outer peripheral surfaces of the fixing roller 24 and the pressure roller 26, respectively. In particular, one end portion of the upper paper ejection guide plate 40A separates the fixed sheet from the fixing belt 32, so that both paper ejection guide plates 40A
It is defined as a peeling guide member 70 that guides in the direction of the discharge port 60 defined from the other end of A and 40B. The peeling guide member 70 and the fixing roller 24 are wound around the peeling guide member 70, the details of which will be described later. The size of the gap between the fixing belt 32 and the portion thereof constitutes a feature of the present invention and is strictly defined.

Here, the fixing roller 24 is configured as an elastic roller, while the pressure roller 26 is configured as a roller having a higher hardness than the elastic roller. On the other hand, the swing bracket 20 includes the first coil spring 3
4, the pressure roller 26 is urged to rotate around the support shaft 22 in the direction in which the pressure roller 26 is pressed against the fixing roller 24. As a result, at the rolling contact portion (nip portion) between the fixing roller 24 and the pressure roller 26, the rolling roller and the rolling roller contact each other with a predetermined pressure contact force, whereby the fixing roller 24 is recessed at the rolling contact portion. Will be brought to. That is, the nip width is set to be sufficiently secured.

The fixing device 10 is provided between each end of the sliding bracket 18 and the corresponding side plate 16,
A second coil spring 36 is further provided for urging the heating roller 28 in a direction away from the fixing roller 24 and applying a predetermined tension to the fixing belt 32. The second coil springs 36 are provided in front and rear pairs at the left and right ends, respectively.

Further, a take-in guide plate 38 for guiding the unfixed sheet toward the rolling contact portion is attached to the above-mentioned housing 12, and the fixing operation is completed after passing through the rolling contact portion as described above. Finished sheet exit port 6
Paper discharge guide plates 40A and 40B that convey the paper toward 0 are attached. Further, the housing 12 is a portion of the outer peripheral surface of the fixing roller 24 where the fixing belt 32 is not wound, and is located immediately upstream of the rolling contact portion with respect to the rotation direction of the fixing roller 24. A thermistor 42 is attached to detect the surface temperature of the affected portion. Here, in this embodiment, the thermistor 42 employs a contact type structure in which the surface temperature of the detected portion is detected by contacting the surface of the detected portion.

The temperature detection position of the thermistor 42 is not limited to the above-mentioned outer peripheral surface of the fixing roller 24 and the portion where the fixing belt 32 is not wound. The outer peripheral surface of the rotating fixing belt 32 may be attached so as to detect the surface temperature of a portion located immediately upstream of the rolling contact portion with respect to the rotation direction of the fixing roller 24. .
In this case, the thermistor 42 is preferably a non-contact type.

The leading end of the unfixed sheet that has been conveyed toward the fixing device 10 via a conveyance mechanism (not shown) first touches the upper surface of the take-in guide plate 38, and is slanted upward while being guided by this. Further, the unfixed sheet guided by the take-in guide plate 38 first comes into contact with the outer peripheral surface of the pressure roller 26 and then the outer peripheral surface of the pressure roller 26. It is set so as to be guided along the rolling contact portion between the fixing roller 24 and the pressure roller 26.

In the fixing device 10 having the above-described configuration, the unfixed sheet S conveyed onto the take-in guide plate 38 via the conveying mechanism (not shown) takes in the lower surface on which the unfixed toner is not adhered. While being contacted and supported by the guide plate 38, the fixing belt 32 is guided toward the rolling contact portion (nip portion) between the fixing roller 24 and the pressure roller 26 around which the fixing belt 32 is wound, and the fixing rollers 24 and 26 are pressed against each other. By being inserted in this state, the unfixed toner is thermocompression-bonded and fixed on the sheet.

The above-mentioned various components will be described individually in sequence below. {Description of Fixing Roller 24} In the fixing roller 24 described above, a bearing 44 (shown in FIG. 2) is provided on the side plate 16.
A cored bar portion 24A is rotatably supported by a roller main body 24B coaxially arranged around the cored bar portion 24A and around which the fixing belt 32 is wound. The roller outer diameter of the fixing roller 24 is set to 35.0 mm in this embodiment. Here, in this embodiment, the cored bar portion 24A is formed of an iron shaft having a diameter of 20 mm, and the roller body 24B is connected to the cored bar portion 24.
It is formed of a silicone rubber heat-resistant elastic body (specifically, 23 degrees in Asuka C hardness on the roller) attached to the outer periphery of A with a thickness of 7.5 mm.

As shown in FIG. 2, a first driven gear 46 is coaxially attached to a shaft portion located at one end of the cored bar portion 24A via a one-way clutch 48, the details of which will be described later. The first driven gear 46 is meshed with a second driven gear 50 coaxially attached to one end of a metal core portion 26A of the pressure roller 26, which will be described later. On the other hand, although not shown in detail, the second driven gear 50
A drive gear that constitutes a part of the drive mechanism is meshed with. In this way, the driving force from the drive mechanism is transmitted to the second driven gear 50 as a counterclockwise rotational force in FIG. 1 via this driving gear, and subsequently to the first driven gear 46, the timepiece shown in the figure. The rotational force in the direction is transmitted to the fixing roller 24 via the one-way clutch 48.

{Description of One-Way Clutch 48} The one-way clutch 48 allows rotation of the fixing roller 24 in the clockwise direction in the figure with respect to the first driven gear 46, but in the counter-clockwise direction in the figure. It is configured to lock relative rotation, in other words, to integrally rotate both. That is, the fixing belt 32 is the pressure roller 26.
The fixing roller 24 is frictionally engaged with the fixing belt 24.
2 is frictionally engaged with the fixing roller 2 by the pressure roller 26.
4 and the fixing belt 32 are driven (rotated together), the peripheral speed of the fixing roller 24 rotating clockwise in the drawing is
The peripheral speed of the pressure roller 26 is the same as that of the pressure roller 26, and the rotation of the fixing roller 24 is set to be slightly faster than the rotation of the first driven gear 46.

{Explanation of Pressure Roller 26} As described above, the pressure roller 26 includes the core metal portion 26A rotatably supported by the side plate 16 through the bearing 54 and the outer periphery of the core metal portion 26A. And a roller body 26B arranged coaxially with the roller main body 26B, and the roller outer diameter is set to 36 mm. Here, in this embodiment, the cored bar portion 26A is
The roller body 26B is formed of an iron pipe having an outer diameter of 33 mm and a wall thickness of 1.5 mm, and the roller body 26B is attached to the outer periphery of the core metal portion 26A with a thickness of 1.5 mm.
(Specifically, the ASKER C hardness is 74 to 75 degrees on a roller harder than the fixing roller 24 described above)
Are formed from.

As described above, the second driven gear 50 is coaxially fixed to the shaft portion disposed at one end of the cored bar portion 26A, and the second driven gear 50 has the above-mentioned structure. The first driven gear 46 meshes with each other, and the driving force from the first driven gear 46 is directly transmitted to the second driven gear 50 via a drive gear (not shown), so that the pressure roller 26 is opposite to the fixing roller 24. Is configured to be rotationally driven in the counterclockwise direction.

In this embodiment, the pressure roller 26 is set as the main drive for conveying the unfixed sheet, and the peripheral speed of the fixing roller 24 is increased even when the fixing roller 24 is thermally expanded. The gear ratios of the first and second driven gears 46 and 50 are set so as not to become higher than the peripheral speed of the pressure roller 26. That is, the rotation speed when the fixing roller 24 is rotated by the first driven gear 46 is the same as that of the fixing belt 32.
It is set so as to be slightly slower than the rotational speed at which the pressure roller 26 is frictionally engaged with and rotated by the pressure roller 26.

On the other hand, in this embodiment, the pressure roller 26 is not located immediately below the fixing roller 24, but is located in the conveyance direction of the unfixed sheet rather than below the fixing roller 24. When the line segment passing through both the center points of the heating roller 28 and the fixing roller 24 is used as the base line, the base line, the fixing roller 24, and the pressure roller 26 are disposed along the downstream side. It is arranged at a position such that the angle formed by a line segment passing through both center points of is a predetermined acute angle. The line segment passing through the center points of both the fixing roller 24 and the pressure roller 26 is set to be substantially orthogonal to the transport direction of the unfixed sheet.

{Explanation of Heating Roller 28} In this embodiment, the heating roller 28 incorporating the above-mentioned first heating source 30 has an outer diameter of an iron pipe cored bar having a diameter of 18 mm and a wall thickness of 0.1 mm. The surface is coated with a PTFE coating layer having a thickness of 20 μm. That is, the heating roller 28 is configured to have a thin cored bar for the purpose of shortening the warming-up time as described later. Both ends of the heating roller 28 are rotatably supported by bearings 56. Inside each bearing 56, a collar 58 made of heat-resistant polyetheretherketone (PEEK) is used as a stopper resin. As a result, the fixing belt 32 is prevented from meandering and deviation during endless running.

A heating source 30 as a heat generating means is built in the inside of the heating roller 28. In this embodiment, the heating source 30 is composed of a halogen lamp having a maximum output of 800 W. There is.

{Explanation of the fixing belt 32} The fixing belt 32 is 1 square cm of the fixing belt 32 so that the unfixed toner on the unfixed sheet S can be fixed to the fixing temperature without giving an excessive amount of heat. The heat capacity per unit is 0.
Those in the range of 002 cal / ° C to 0.025 cal / ° C are preferable.

Therefore, in this embodiment, FIG.
As shown in FIG. 3, the fixing belt 32 includes an endless belt base 32a made of polyimide resin having an inner diameter of 50 mm and a thickness of 70 μm, and a PFA having a thickness of 30 μm coated on the outer peripheral surface (surface layer) of the belt base 32a. And the heat-resistant release layer 32b. The conductive PFA heat-resistant release layer is effective for preventing the belt surface layer from being charged. Further, in order to improve the fixing image quality, the belt base material 32a
There is a case where an elastic layer made of silicone rubber or the like having a thickness of 300 μm is directly coated on the outer peripheral surface of the. In this case, the PFA heat-resistant release layer 32b is coated on the outer peripheral surface of the elastic layer.

It is needless to say that the present invention is not limited to the use of the polyimide resin as the belt base 32a in this way, and a nickel electroformed metal belt can be used. When the nickel electroformed metal belt is used as the belt base 32a, the thickness of the belt base 32a is, for example, 4 mm.
The surface of the belt base 32a is coated with a heat-resistant silicone rubber with a thickness of 300 μm.
Further, on the outer periphery of this heat-resistant silicone rubber layer, as in the case where the material of the belt base 32a is polyimide resin, a thickness of 3
A structure is adopted in which the heat-resistant release layer 32b made of PFA and covered with 0 μm is coated.

{Explanation of Tension Applying Mechanism to Fixing Belt 32} As described above, in this embodiment, as a mechanism for applying tension to the fixing belt 32, the heating roller 28 is separated from the fixing roller 24. The second coil spring 36 that biases the second coil spring 36 is provided.

That is, the heating roller 28 is urged through the sliding bracket 18 by the urging force of the second coil spring 36.
The fixing belt 32, which is biased in the direction away from the fixing roller 24 and is endlessly stretched between the heating roller 28 and the fixing roller 24, is stretched in a tensioned state with a predetermined tension.

As described above, by the action of the second coil spring 36, the fixing belt 32 frictionally engages with the pressure roller 26 and rotates together, and in accordance with the rotation of the fixing belt 32, the fixing roller 24 rotates. Is driven by the fixing belt 32 in a stable state without slipping or loosening.

{Explanation of the peeling guide member 70} Next, the peeling guide member 70, which is a feature of the present invention, will be described in detail. As shown in FIG. 4, the peeling guide member 70 is defined from one end portion of the upper paper ejection guide plate 40A, in other words, is fixedly arranged with respect to the housing 12. Further, the one end portion of the lower paper ejection guide plate 40B is separated so that the gap from the outer peripheral surface of the corresponding pressure roller 26 is not controlled, and this does not contact the outer peripheral surface of the pressure roller 26 without mistake. It suffices that the state of being close (that is, close to) is achieved, but the peeling guide member 70 defined from one end of the upper sheet ejection guide plate 40A and the outer peripheral surface of the fixing belt 32 corresponding thereto. In this embodiment, the gap G between and is accurately controlled to be 1.0 mm in order to reliably achieve the peeling function.

Further, in this embodiment, the peeling guide member 70 is arranged so as to be separated from the outer peripheral surface of the corresponding fixing belt 32 over the entire area. More specifically, the peeling guide member 70 has an edge 70a which is set closest to the outer peripheral surface of the fixing belt 32 and which is set parallel to the rotation axis of the fixing roller 24. The gap G from the outer peripheral surface of the belt 32 is accurately specified to be 1.0 mm as described above.

Here, as shown in FIG. 5, the disposition position of the separation guide member 70 is such that the end edge 70a, which is the part defining the 1.0 mm gap G in the separation guide member 70, is located at this position. A line segment L1 connecting the center position of the fixing roller 24, the center position of the fixing roller 24 and the pressure roller 2
An angle θ1 formed by a line segment L0 connecting the center position of 6 is set to 55 degrees in this embodiment.
Further, an angle θ formed by a line segment L2 connecting the center position of the fixing roller 24 and the exit end position of the nip and the line segment L0 described above.
2 is set to 13 degrees in this embodiment. The angle θ2 is approximately half the nip angle (the angle corresponding to the central angle of the fixing roller 24, which allows for the nip width).

Considering the optimum range of the angle θ1, if the angle θ is smaller than 30 degrees, the edge 70a of the peeling guide member 70 comes too close to the exit of the rolling contact portion, and the leading edge of the fixed sheet is fixed. This is because there is a risk that the end edge 70a may come into contact with the end edge 70a to be damaged or jammed. Also, the angle θ
Is larger than 60 degrees, the toner image once fixed on the sheet while passing through the rolling contact portion is again touched with the fixing belt 32 and reheated, and an offset phenomenon occurs due to partial melting. There is a possibility that it may be caused, and there is also a possibility that the time for which it adheres to the fixing belt 32 before it is peeled off may increase and the curl becomes large, which is not preferable.

From the above viewpoint, in this embodiment,
The optimum range of the angle θ1 is 30 degrees to 60 degrees, and 55 degrees in this embodiment is actually within this optimum range.

Next, the optimum range of the gap G will be verified. For this verification, the inventor of the present invention set the gap G to 5 types from 0.5 mm to 2.5 mm in 0.5 mm increments, and measured the peelability in each gap. The measurement results are shown in Table 1.

[0053]

[Table 1]

In Table 1, "○" indicates that there was no problem in peelability, "△" indicates that the peelability was not sufficient, but there was no problem in actual use, and "x". Indicates that there was a problem in peelability (that is, peeling could not be performed). As the measurement condition (paper passing condition), the sheet conveying speed (linear speed) is 210 mm / sec.
And the pressure applied by the pressure roller 26 is 22 Kgf /
One side, nip width at rolling contact is 10.0 mm
The surface temperature of the fixing belt 32 is about 10.5 mm.
The temperature is 150 ° C. to 155 ° C., and the surface temperature of the pressure roller 26 is 125 ° to 135 ° C. As the sheet, 55 kg of plain paper (64 g / square m) was used, and as the toner, Docu PRINT made by XEROX was used.
A toner for C620 was used.

As is clear from Table 1, in the numerical value of the gap G, the smaller the lower limit value, the better. However, as the upper limit value, the fixing of the solid image at the leading edge in the A4 longitudinal feed is performed. From the viewpoint of poor peelability of the finished sheet, 2.0 mm is judged to be a level that causes no problem in practical use.

As described above, the lower limit value may be as small as possible, but the variation of the outer diameter of the fixing roller 24 (the minimum diameter is about ± 0.1 mm, the minimum swing width is about 0.1 mm). ) And the variation of the peeling guide member 70, it is judged that at least 0.2 mm is necessary to reliably maintain the non-contact state with the outer peripheral surface of the fixing belt 32. As a result, the optimum range of the gap G is 0.2 mm to 2.0 mm,
The 1.0 mm in this example is actually within this optimum range.

As described above, the fixing device 10 of this embodiment
With the above configuration, even if the fixed sheet that has passed through the rolling contact portion and undergoes the fixing operation comes into close contact with the outer peripheral surface of the fixing belt 32, it is conveyed in synchronization with the traveling of the fixing belt 32. Then, the peeling guide member 70 is reached,
As a result, the fixing belt 32 is separated from the outer peripheral surface and is guided toward the discharge port 68.

As a result, according to this embodiment, even in the oilless state, the fixed sheet is reliably peeled from the outer peripheral surface of the fixing belt 32 after being subjected to the fixing operation, and is discharged from the discharge port 60. As a result, the oilless effect can be fully exerted.

Needless to say, the present invention is not limited to the configuration of the above-described embodiment, but can be variously modified without departing from the scope of the present invention.

For example, in the above-described embodiment, the oilless roller for applying the releasing oil to the outer peripheral surface of the fixing belt 32 is not provided, and the oilless structure is described. Needless to say, the configuration is not limited to the configuration in which the oil application roller is not provided, and a configuration in which the oil application roller is provided may be adopted. In this case, since the oil applying roller comes into pressure contact with the fixing belt 32 with a predetermined pressure contact force,
It can be used in cooperation with the second coil spring 36 as the tension applying means described above, or can be used in place of the second coil spring 36.

Further, in the above-described embodiments, the core metal 28a of the heating roller 28 is described as being formed of an iron pipe, but the present invention is not limited to such a configuration, and SUS is used. Needless to say, the pipe may be made of stainless steel or aluminum pipe.

Further, in the above-mentioned embodiment, it is explained that only the heat source 30 built in the heating roller 28 is provided as the heat generating means, but the present invention is not limited to such a constitution, and is described above. The pressure roller 26 may be configured so as to include a second heating source incorporated therein. In this case, the second heating source may be a halogen lamp of, for example, 250 W whose maximum output is set smaller than that of the heating source 30 built in the heating roller 28.

It is needless to say that the heating source 30 may use a planar heating element in addition to the halogen lamp as described above. That is, its heat generation type,
It goes without saying that the shape of heat generation is not limited at all.

Further, in the above-described embodiment, the peeling guide member 70 is described as being fixedly constructed from the tip portion of the upper sheet discharge guide plate 40A, but the present invention has such a construction. Without being limited thereto, as shown in FIG. 6 and FIG. 7 as another embodiment, it may be rotatable.

The structure of another embodiment of the peeling guide member will be described below with reference to FIGS. 6 and 7. In the following description, the same parts as those in the above-described embodiment are designated by the same reference numerals and the description thereof will be omitted.

First, as shown in FIG. 6, a separation guide member 80 according to another embodiment is a holder rotatably supported around a support shaft 82 set parallel to the rotation axis of the fixing roller 24. 84 and a peeling guide plate 88 attached to the lower surface of the holder 84 via screws 86 located outside the paper passing area, and between the holder 82 and the side plate 16.
A coil spring 90, which urges the holder 82 to rotate in the counterclockwise direction in the drawing, is spanned.

Here, as shown in FIG. 7, the peeling guide plate 88 is constructed so as to have a non-contact portion / contact portion in accordance with the paper passing area / non-paper passing area of the fixing belt 32. There is. More specifically, the fixing belt 32 has a paper passing area 32 with which the unfixed sheet comes into contact when the unfixed sheet is passed.
B is defined in the central portion excluding both side edges, and non-sheet passing areas 32A where the unfixed sheet does not come into contact are defined in both side portions, respectively.

In the state where the fixing belt 32 is defined in this way, the peeling guide plate 88 comes into contact with the fixing belt 32 at both end portions facing the non-sheet passing area 32A of the fixing belt 32, as shown in the drawing. With a portion 88A,
In the central portion of the fixing belt 32, which faces the sheet passing area 32B, a non-contact portion 88B which is not in contact with the fixing belt 32 is provided.

In other words, the tip surface 88a of the contact portion 88A.
Is set so as to come into contact with the outer peripheral surface of the non-sheet passing area 32A of the fixing belt 32, and the tip surface 88b of the non-contact portion 88B.
Is set so as to be separated from the outer peripheral surface of the sheet passing area 32B of the fixing belt 32 by a gap G. In this way, even if the fixed sheet that has passed through the rolling contact portion is adhered to the outer peripheral surface of the fixing belt 32, the peeling guide member 8 is moved as the fixing belt 32 runs.
0, the leading end of the fixed sheet comes into contact with the lower surface of the peeling guide plate 88 and is peeled from the outer peripheral surface of the fixing belt 32, and the same effect as the above-described embodiment. Will be able to play.

In this embodiment, the peeling guide plate 8 is urged by the rotating biasing force of the coil spring 90 described above.
The contact portion 88A of No. 8 is always in contact with the outer peripheral surface of the fixing belt 32. As a result,
The non-contact portion 88 </ b> B of the peeling guide plate 88 is always reliably separated from the outer peripheral surface of the fixing belt 32 by the gap G.

Here, at least the contact portion 88A of the peeling guide plate 88 is made of a heat resistant resin having slidability, for example,
It is composed of Teflon (registered trademark) resin. Alternatively, at least the contact portion 88A of the peeling guide plate 88
Is covered with a fluororesin. As a result, even though the non-sheet passing area 32A, the contact portion 88A
Therefore, it is possible to suppress the influence of the contact between the two as much as possible.

[0072]

As described above in detail, according to the present invention, there is provided a fixing device capable of reliably peeling the fixed sheet from the surface of the fixing belt.

Further, according to the present invention, there is provided a fixing device capable of surely peeling a solid printed sheet from the surface of the fixing belt without adversely affecting the sheet passing area of the fixing belt. Will be done.

[Brief description of drawings]

FIG. 1 is a front sectional view showing a configuration of an embodiment of a fixing device according to the present invention.

FIG. 2 is a cross-sectional view showing a supporting state at an end portion of each roller in the fixing device shown in FIG.

FIG. 3 is a front view showing the configuration of the fixing belt.

FIG. 4 is a diagram for explaining a gap G between a peeling guide member and a fixing belt.

FIG. 5 is a diagram for explaining an arrangement position of a peeling guide member.

FIG. 6 is a front view showing the configuration of a peeling guide member according to another embodiment.

FIG. 7 is a diagram showing the peeling guide member shown in FIG. 6 as viewed from below.

[Explanation of symbols]

10 Fixing Device 12 Housing 14 Bottom Plate 16 Side Plate 18 Sliding Bracket 20 Swing Bracket 22 Spindle 24 Fixing Roller 24A Core Bar 24B Roller Body 26 Pressure Roller 26A Core Bar 26B Roller Body 28 Heating Roller 30 Heating Source 32 Fixing Belt 32a Belt base 32b Heat-resistant release layer 32A Non-paper passing area 32B Paper passing area 34 First coil spring 36 Second coil spring 38 Intake guide plate 40A; 40B Paper discharge guide plate 42 Thermistor 44 Bearing 46 First driven gear 48 One-way clutch 50 Second driven gear 54 Bearing 56 Bearing 58 Collar 60 Discharge port 70 Peeling guide member 80 Peeling guide member (other embodiment) 82 Spindle 84 Holder 86 Screw 88 Peeling guide plate 88A Contact part 88B Non-contact Part 88a Contact part 88A Tip surface 88b of the non-contact portion 88B, the coil spring G, the gap L0, the line segment L1 connecting the centers of the fixing roller 24 and the pressure roller 26, and the edge 70a of the peeling guide member 70 and the center position of the fixing roller 24. Line segment L2 Line segment connecting the center position of the fixing roller 24 and the tip position of the exit of the nip portion

Claims (11)

[Claims] 1. A fixing roller, a pressure roller for rolling contact with the fixing roller at a predetermined pressure, a heating roller arranged apart from the fixing roller, and an endless member for hanging the heating roller and the fixing roller. The fixing belt that has been passed over and a heating unit that heats the fixing belt to heat the unfixed toner on the sheet that passes through the rolling contact portion of the fixing roller and the pressure roller are provided. In a fixing device for fixing the unfixed toner onto the sheet by passing the sheet carried on the sheet along the one direction in the fixing device, the sheet is carried downstream from the rolling section in the traveling direction of the sheet. On the side, a peeling guide member that peels the fixed sheet from the fixing belt and guides it in the exit direction is provided, and the gap between the peeling guide member and the sheet passing area of the fixing belt is 0. A fixing device characterized in that it is set to 2.0mm or less in the range of 2 mm. 2. The fixing device according to claim 1, wherein the peeling guide member is constituted by a part of a paper discharge guide plate. 3. The fixing device according to claim 2, wherein the peeling guide member is fixedly disposed. 4. The fixing device according to claim 2, wherein the peeling guide member is spaced apart from the outer peripheral surface of the fixing belt over the entire area. 5. The peeling guide member includes a non-contact portion arranged to face a sheet passing area of the fixing belt, and a contact portion arranged to face a non-sheet passing area of the fixing belt. The fixing device according to claim 1, further comprising: 6. The fixing device according to claim 5, wherein the contact portion of the peeling guide member is formed of a heat resistant resin having slidability. 7. The fixing device according to claim 5, wherein the contact portion of the peeling guide member is covered with a fluororesin. 8. The peeling guide member is rotatably supported about an axis parallel to the rotation axis of the fixing roller, and urged so that the contact portion comes into contact with a non-sheet passing area of the fixing belt. The fixing device according to claim 5, wherein the fixing device is urged to rotate by a member. 9. A portion of the peeling guide member which defines the gap connects a line segment connecting the gap and the center position of the fixing roller, and a center position of the fixing roller and a center position of the pressure roller. The angle with the line segment is 30 to 60
The fixing device according to claim 1, wherein the fixing device is set to be within a range of degrees. 10. The fixing device according to claim 1, wherein a release layer is provided on the outermost periphery of the fixing belt. 11. The fixing device according to claim 10, wherein the release layer includes a fluororesin.